In sharp contrast to the rapidly developing technology in many other fields, construction technology has proceeded at a relatively slow pace over the last half-century. Although numerous techniques have been developed, these have not been adopted widely by the construction industry with the result that construction has remained labor intensive and of a handicraft nature. Accordingly, housing and building costs have remained very high.
Prefabrication has been cited as one of the potential answers to the problem, but many of the proposals to date have not proven to be commercially successful and relatively few prefabrication techniques have been adopted by the industry. Prefabrication techniques fall under two major categories, namely, light wood and aluminum frame prefabrication, and concrete or like product precasting. Wood and aluminum frame prefabrication is limited to low density suburban housing. Concrete prefabrication is more appropriate for urban buildings due to fire and structural safety requirements.
The majority of the concrete precasting prefabrication systems, many of which were designed in Europe, have not been commercially successful, particularly in North America. Most are structural systems and not housing or building systems. While structural i.e. walls, floors, they do not incorporate functional attributes related to housing building users' needs and architectural understanding. In addition to not being user or market oriented to any substantial degree, these known systems tend to be costly, requiring expensive prefabrication factories and relatively expensive handling and erection equipment and techniques. To be viable such concepts usually require a very high degree of repetition.
Most of the prior art concrete prefabrication systems follow one of three primary conceptual types, namely:
(1) a shear wall and floor plate design; primarily high rise, with the innovative part of the design being concentrated around the connection details. Erection usually requires shoring and bracing. These systems tend to produce a heavy structural box which has no particular relationship to any specific end use. These structures require finishing, further partitioning and outfitting with traditional add-on methods and equipment.
(2) a three-dimensional concrete box; like the shear wall system noted above, the use of the space within such stacked boxes is arbitrary and the end use and function has to be created by an add-on system of traditional finishes, partitions and equipment.
(3) on site systems of either large, portable forms for pouring in place, or wire cages and walls with the concrete sprayed on and then trowelled on-site. These systems do not require expensive factories and handling equipment; however, they do require skilled on-site labor and the system is capable of providing only the macro-space. All finishes and equipment must then be added in the traditional fashion.
A variety of patents have issued over the years relating to various types of prefabricated units or slabs intended to be assembled into a building or other structure. One common problem which remained largely unsolved was that they were closed systems with limited architectural flexibility and space flexibility.
Another form of building construction is a variation of type (1) above and involves the use of shear walls of shallow U-shaped cross-section. Examples of patented processes and construction module configurations of this type are described in U.S. Pat. No. 3,952,471 to Mooney, and U.S. Pat. No. 4,142,340 to Howard. The Mooney patent essentially discloses a building structure having a series of vertical precast combination foundation wall and side wall panels of shallow U-cross section supported on a footing at spaced apart intervals. This structure includes in-fill panels with cast-in windows and doors. The in-fill panels are connected by welding between load-bearing vertical side edge flanges of the wall panels. This system provides only an exterior wall arrangement.
The building construction scheme described in the Howard patent employs a series of standard panels each having a shallow U-shape cross-section. The walls are formed by a series of such panels disposed vertically in side-by-side relationship. Because of their instability, as is the case of the Mooney panels, the panels must be temporarily braced during erection and then permanently connected to each other by fastener elements. In the Howard scheme, a plurality of side fastener elements which bridge the panels are employed. In essence, the Howard configuration involves an exterior wall system which works in conjunction with a predetermined roof system. A somewhat specialized footing is also required to provide for connection to the vertical exterior wall panels. In the construction arrangements described by both Howard and Mooney, neither module performs a volumetric, space enclosing function related to architectural requirements.